Machine and method for balancing a member during rotation

ABSTRACT

A machine for balancing a rotating member includes hard bearing balancing apparatus for determining the magnitude and circumaxial location of imbalance. A sensor responds to the position of the rotating member. A computer receives signals from the balancing apparatus and the sensor and determines the location of one or more projectiles to be fired at the member. A firing mechanism including a piezoelectric actuator fires the projectiles in timed relationship with the rotation of the member so as to position the projectiles as required for balancing.

BACKGROUND OF THE INVENTION

Attempts to balance members during rotation have not been commercially successful in the past. Accordingly, it is the general object of the present invention to provide a machine for balancing a member during rotation in a procedure much more expeditious and at least as accurate as manual balancing and which is highly efficient and reliable over a long service life.

RELATED APPLICATIONS

The filing date of Provisional Application entitled Method and Apparatus for Balancing Fan and Blower Assemblies filed Jan. 9, 2004 is hereby claimed for the present application a nd the Provision Application is hereby incorporated herein by reference.

U.S. patent application entitled A Rotatable Member with an Annular Groove for Dynamic Balancing During Rotation filed Jan. 9, 2004 is hereby incorporated herein by reference.

SUMMARY OF THE INVENTION

In fulfillment of the aforementioned object and in accordance with the present invention, a machine for balancing a rotating member comprises apparatus for determining the magnitude and the circumaxial location of the imbalance of the member. A sensor responsive to the position of reference mark on the rotating member is also provided together with at least one balancing projectile of known weight. A computer is connected with and receives signals from the first mentioned apparatus and the sensor and determines the location of one or more projectiles to be fired at the member in timed relationship with rotation of the member whereby to balance the same within a specified tolerance. A fast acting firing mechanism comprises an electrical-mechanical transducer assembly with a reaction time compatible with the speed of rotation of the rotating member is operated by the computer to fire a projectile at the member at the circumaxial location determined by the computer. The balancing machine of the invention is compatible with rotational speeds of a member to be balanced in both lower speed ranges below 1000 R.P.M. as well as higher speeds at least up to 5000 R.P.M.

Operation at high speed and with a high degree of accuracy, as much as five times that achieved manually, is attributable at least in part to the use of a piezoelectric stack as a transducer-actuator for receiving an electrical signal from the computer and rapidly converting to a mechanical signal for triggering a momentary valve which releases an explosive burst of air for propelling a projectile toward the rotating member. While it is anticipated that future piezoelectric stack actuators with enhanced output characteristics will accommodate system designs wherein the actuator directly triggers a momentary valve, or perhaps employs a motion amplifier along, the presently preferred design includes a motion amplifier in the form of a lever and a force amplifier in the form of a stored energy device operated by the lever. A loading mechanism operable in timed relationship with the firing mechanism includes a shuttle movable from a loading position to a firing position and which has a chamber for receiving and transporting projectiles and for positioning projectiles to be propelled by the explosive burst of air mentioned above. In the firing position of the shuttle, a through opening communicating with the chamber is open at one end to the momentary valve for receipt of the burst of air and that other end for the discharge of projectiles toward the rotating member. A magnet in the shuttle forms a means for retaining projectiles in position in the chamber during transfer and prior to discharge.

A vibratory feeder and supply tube deliver projectiles to the loading mechanism at the loading position.

Finally, the method of the invention comprises the steps of determining the location of imbalance of a rotating member, calculating the amount and position of balancing weight required to balance the member, calculating the time to fire based on speed of rotation and total firing time, and firing one or more projectiles as required at the member to balance the same.

When the weight required to balance a rotating member is not an integral number of projectiles, the method requires a further determination of two or more locations which are spaced circumaxially from the point of imbalance but which will balance the member. Projectiles are then fired at these locations.

The aforementioned condition may occur when less than a single projectile is required at the point of imbalance or when a first integral projectile is required at the point of imbalance with additional projectiles required at spaced circumaxial positions for an additional non-integral correction.

DESCRIPTION OF THE DRAWINGS

FIG. 1 of the drawings is a schematic view of the balancing machine of the present invention, and

FIG. 2 are schematic views of the loading mechanism of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, it will be observed that a member to be balanced takes the form of a centrifugal air impeller indicated generally at 10. The impeller 10 is mounted on a conventional apparatus known as a hard bearing balancing machine. Various machines may be employed with a SCHENCK machine presently preferred. The impeller shown is rotated at a constant speed of approximately 1700 R.P.M. but the balancing machine of the invention can accommodate rotational speeds from the low hundred to at least 5000 R.P.M. The balancing machine 12 responds to unbalanced forces and reports to a computer 14 via broken line 16 advising as to the magnitude and circumaxial location of imbalance of the impeller 10. Sensor 18, preferably a diffuse laser sensor, responds to instantaneous position of the impeller which is provided with a reference mark legible to the sensor and advises the computer accordingly.

The computer 14 employing the information from the balancing apparatus and the sensor, and considering the known weight of the balance projectiles, calculates the required number of projectiles and their respective circumaxial locations to balance the rotating member. The computer thus determines the precise instant in time to send a signal 22 to piezoelectric stack transducer-actuator 20 to discharge a projectile so that it will engage the rotating member at the desired location. All time lags resulting from operation of the piezoelectric stack and other elements to be described below are considered by the computer with precise positioning of the projectile resulting. An appropriately programmed computer should be of a high-speed type but may be conventional.

The piezoelectric transducer-actuator stack 20 has an exceptionally high reaction time.

Mechanical output element 24 of the actuator 20 is operatively associated with the right hand end of lever 26 in FIG. 1 which has a pivot point 28 providing for amplification of the output movement of the element 24. At its left hand end, the lever 26 has a small detent 30 engaging a pin 32 on a spring-loaded striker 34 shown in FIG. 1 in an armed or cocked position. The striker 34 serves as a force amplification means and carries a small pin 36 which engages a trigger pin 38 on a momentary valve 40 when the recess 30 is pivoted downwardly slightly releasing the pin 32 and permitting the striker to rotate in a counter-clockwise direction. The striker 34 is returned to its armed position by a small pneumatic rotary actuator, not shown, but which is connected to and operated by the computer 14 by broken line 39.

Momentary valve 40 which may be conventional serves to release an explosive burst of air to a firing chamber 41 in a loading mechanism 44 best illustrated in FIG. 2. Supply conduit 42 extending from the valve communicates with a source of air under pressure.

Referring now more particularly to the loading mechanism 44 in FIG. 2, a shuttle 46 moves between loading and firing positions illustrated respectively in the left and right hand views in FIG. 2. In the left hand view with the shuttle in the loading position, a projectile is shown in the shuttle chamber 41 having been delivered by a tube 50, FIG. 1, which extends from a vibratory feeder 52. A magnet 54 holds the projectile in position in the chamber, it being noted that a right portion of the chamber is somewhat smaller than a left hand portion thereof with the projectile approximately fitting the said left hand portion. It should also be noted that the chamber has a through opening which communicates with the supply tube 50 at the left in the left hand view and with a projectile discharge barrel 56 in the right hand view. Further in the right hand view, the chamber 41 communicates at the right with the valve 40, not shown in FIG. 2, for receipt of the burst of air as aforesaid.

Air cylinder 58 transfers the shuttle 46 between loading and firing positions under the control of the computer 14 via broken line 60. As mentioned, projectiles are delivered to the chamber 41 and are held in position by magnet 54. The projectiles are preferably metallic and at the present time small bearings or BB's of the type used in a powered BB gun may be used. The weight of the projectiles is of course determined and entered in the computer memory.

As the shuttle is moved downwardly to its firing position the chamber 41 is sealed by small annular seals 62 and 64 respectively above and below the chamber which cooperate with a slightly tapered housing opening in which the shuttle slides. Thus, at the firing position in the right hand view of FIG. 2, the chamber 41 is conditioned to receive the air burst from the valve 40 whereupon the projectile therein is propelled toward the impeller 10, FIG. 1. Exit sensor 58 reports successful firings to the computer 14 via broken line 59 and may be employed to determine the response time of the firing mechanism.

On reaching the impeller 10, the projectile is captured and retained in position by an annular groove 66 best shown in FIG. 1 and more fully described an illustrated in the above-mentioned U.S. Application.

From the foregoing it will be apparent that the balancing machine of the present invention as a whole has an exceptionally fast reaction time, due in large part to the incorporation of the piezoelectric actuator, as well as extremely high accuracy characteristics, this due at least in part to the incorporation of a high speed computer. The total time in balancing a rotating member with the machine of the present invention may be as little as one tenth that required in a manual balancing procedure. It is also to be noted, as mentioned above, that the accuracy balancing achieved with the machine may be as high as five times that realized in manual balancing. 

1. A machine for balancing a member during rotation comprising apparatus for determining the magnitude and the circumaxial location of the imbalance of the member, a sensor responsive to the position of the rotating member, at least one balancing projectile of a known weight, computer means connected with and receiving signals from the measuring apparatus and sensor and determining the location of one or more balancing projectiles to be fired at the rotating member in timed relationship with the rotation of the member whereby to balance the member within a specified tolerance, a fast acting firing mechanism comprising an electrical-mechanical transducer assembly with a reaction time compatible with the speed of rotation of the rotating member connected with and responsive to the computer and operable to fire a projectile at the member in response to a signal from the computer to satisfy the need for a balancing weight at the computer determined circumaxial location
 2. A machine for balancing a rotating member as set forth in claim 1 wherein the reaction time of the firing mechanism is compatible with rotational speed of the rotating member up to 5000 R.P.M.
 3. A machine for balancing a rotating member as set forth in claim 1 wherein the reaction time of the firing mechanism is compatible with rotational speed of the rotating member up to 1000 R.P.M.
 4. A machine for balancing a rotating member as set forth in claim 1 wherein the electrical-mechanical transducer takes the form of a piezoelectric stack.
 5. A machine for balancing a rotating member as set forth in claim 4 wherein a motion amplifier is interposed between the piezoelectric stack and the firing device to amplify the motion output of the former.
 6. A machine for balancing a rotating member as set forth in claim 5 wherein a mechanical means is interposed between the piezoelectric stack and a firing device in the firing mechanism to amplify the force of the former.
 7. A machine for balancing a rotating member as set forth in claim 1 wherein the firing mechanism includes a device providing an explosive burst of air for firing a projectile.
 8. A machine for balancing a rotating member as set forth in claim 1 wherein the projectile is a small spherical element.
 9. A machine for balancing a rotating member as set forth in claim 1 wherein the projectile is of metallic construction.
 10. A machine for balancing a rotating member as set forth in claim 1 and including a loading mechanism operable in timed relationship with the firing mechanism to feed projectiles to the latter seriatim.
 11. A machine for balancing a rotating member as set forth in claim 10 wherein the loading mechanism includes a shuttle movable between loading and firing positions in timed relationship with the firing mechanism.
 12. A machine for balancing a rotating member as set forth in claim 11 wherein the shuttle includes a magnet which captures a metallic projectile at the loading position of the shuttle and holds the same in position during transfer to the firing position prior to firing.
 13. A machine for balancing a rotating member as set forth in claim 11 wherein a vibratory feeder and feeder tube is provided to supply projectiles to the shuttle at the loading position.
 14. For use in a balancing machine or the like, a high speed electrical-mechanical transducer assembly comprising a piezoelectric stack, and a firing mechanism for a balancing projectile operated by the transducer assembly.
 15. A high-speed electrical-mechanical transducer assembly as set forth in claim 14 wherein a lever is provided to amplify motion output of the piezoelectric stack.
 16. A high-speed electrical-mechanical transducer assembly as set forth in claim 15 wherein a stored energy device is provided and is operated by the lever to provide force amplification of the output signal of the stack and lever.
 17. A high-speed electrical-mechanical transducer assembly as set forth in claim 16 wherein a spring is provided together with a means for arming and a means for releasing the spring, the latter means being operated by the lever.
 18. A high-speed electrical-mechanical transducer assembly as set forth in claim 14 wherein the firing mechanism includes a device providing an explosive air burst for firing a projectile.
 19. A high-speed electrical-mechanical transducer assembly as set forth in claim 18 wherein said device includes a valve triggered by the transducer assembly and a source of air under pressure supplying the valve.
 20. A high-speed electrical-mechanical transducer assembly as set forth in claim 14 and including a loading mechanism operatively associated with the firing mechanism and delivering projectiles seriatim thereto.
 21. For use in a balancing machine or the like having a firing mechanism requiring the delivery in series of small projectiles to a firing position, a loading mechanism comprising a shuttle movable between a loading position and the firing position, means at the loading position supplying projectiles to the shuttle, means for retaining projectiles in position in the shuttle during movement to the firing position, and means for selectively moving the shuttle between said loading and firing positions.
 22. A loading mechanism as set forth in claim 21 wherein the firing position takes the form of a firing chamber forming a part of the firing mechanism.
 23. A loading mechanism as set forth in claim 22 wherein the firing chamber has a through opening and projectiles are fired through one side of said opening.
 24. A loading mechanism as set forth in claim 23 and including means providing an explosive air burst at the opposite side of the opening in said chamber for firing the projectiles from the chamber.
 25. A loading mechanism as set forth in claim 21 and including a feed tube and a vibratory hopper supplying the loading mechanism.
 26. A loading mechanism as set forth in claim 21 wherein the means for retaining the projectiles is a magnet.
 27. A loading mechanism as set forth in claim 21 wherein the means for selectively moving the shuttle between loading and firing positions takes the form of an air cylinder.
 28. A method for balancing a member during rotation comprising the steps of providing a means for securing in position balancing projectiles fired at the member, determining the weight and location required for balancing the member and when the weight is not an integral number of projectiles further determining the positions of two or more projectiles which will balance the member, at least one of said positions being spaced circumaxially from the point of imbalance, and firing two or more projectiles at the positions which will balance the member.
 29. A method for balancing a member during rotation as set forth in claim 28 wherein the weight required to balance the member is determined to be less than that of a single projectile, and wherein two (2) circumaxially spaced projectiles are employed.
 30. A method for balancing a member during rotation as set forth in claim 28 wherein it is determined that at least one projectile is required at the point of imbalance and at least one additional projectile is required in circumaxially spaced relationship therewith, and wherein the projectiles are located accordingly on the member.
 31. A method for balancing a member during rotation comprising the steps of determining the location of the imbalance, calculating the amount and position of balancing weight required to balance the member, calculating the time to fire based on the speed of rotation of the member and the total firing time, firing one or more projectiles as required at the member to balance the same. 